update docs

Author: lkdvos

docs/src/man/algorithms.md

@@ -292,9 +292,7 @@ disadvantages:
   and if the bond dimension is grown slow enough, this still obtains a very good expansion
   scheme. Again, The state will remain unchanged and a one-site scheme will now be able to 
   push the optimization further. The subspace used for expansion can be truncated through
-  `trscheme`, which dictates how many singular values will be added. Additionally, this 
-  method does not project onto the local two-site basis, which might overcome symmetry-based
-  obstructions that can be encountered in the other methods.
+  `trscheme`, which dictates how many orthogonal vectors will be added.
 
 * [`VUMPSSvdCut`](@ref): This algorithm is based on the [`VUMPS`](@ref) algorithm, and
   consists of performing a two-site update, and then truncating the state back down. Because

src/algorithms/changebonds/randexpand.jl

@@ -2,7 +2,9 @@
 $(TYPEDEF)
 
 An algorithm that expands the bond dimension by adding random unitary vectors that are
-orthogonal to the existing state.
+orthogonal to the existing state. This means that additional directions are added to
+`AL` and `AR` that are contained in the nullspace of both. Note that this is happens in
+parallel, and therefore the expansion will never go beyond the local two-site subspace.
 
 ## Fields